[unreadable] Past work has demonstrated that level of cocaine use in heroin-dependent individuals is positively related to increased engagement in HIV-risk taking behaviors. Although the results are promicint, several limitations need to be addressed. A true test would require more separable groups of crack/cocaine and heroin users, to more clearly isolate differences among these drugs. Thus, in the current application we further examine the relationship between cocaine use and HIV-risk taking behaviors, and including a focus on the role of impulsivity-related factors as pathways to drug choice. Specifically, we will study 100 drug users seeking treatment to examine the following: a) differences in risky sexual behavior and HIV risk behaviors across drug groups, and b) the relationship between various constructs of disinhibition to drug preference. Following from these initial results, we will retest participants after treatment to begin to examine the time course of drug use and risky sexual behavior, and its influence on risky sexual behavior after treatment across heroin and crack/cocaine users. [unreadable] [unreadable] [unreadable] [unreadable]